The best place to learn about status matching is at FlyerTalk, specifically the "master" discussion thread and status matches. You can find it here:
http://www.flyertalk.com/forum/milesbuzz/9558-status-match-master-thread.html

Scott is actually very incorrect. Most airlines need a lot more than a copy of your current elite card. They'll want actual proof that you fly a bit (usually a copy of your mileage statement with your current airline).

He's also wrong that "Status matching is more popular than ever." I'm not sure that he has any idea how popular status matching is in comparison to year's past. Certainly, anecdotal evidence suggests that more people matched to Northwest last year because they were generous with status matching, and people knew that getting status on Northwest would eventually equate to status on Delta, which is a little stingier. But other airlines (AA, USAir, United) got stingier with status matches in the past few years, preferring to force travelers into challenges instead.

Furthermore, status matching isn't that easy, and is often not so worthwhile. Scott says, "The game of status matching means you really only need to earn status the hard way once - and after that, smart people can continue holding on to elite status on multiple airlines for several years."

This is blatantly misinformative. First of all, matching status with an airline only works as a one-time thing. I'm an elite with AA. I can certainly status match to Northwest or Alaska, but I won't keep the status with those airlines unless I actually fly on them. And I can't just keep status matching... Almost every airline will only approve a status match once. So yes... status matching can get you fast tracked to mid-tier status on many airlines (very very few match to top-tier), but it will only do you much good for a year. Then you have to re-earn status the hard way.